Helical spring for producing artificial reverberation

ABSTRACT

A helical spring for producing artificial reverberation, with the frequencies to be reverberated being impressed thereon in the form of torsional vibrations, has individual turns, at random locations therealong, deformed irregularly from a normally circular configuration. Portions of the deformed turns may be deformed outwardly from the normally circular configuration or deformed inwardly therefrom, or in both directions, but in the plane of the circular configuration.

United States Patent v [451 -Oct. 10, 1972 F idi [54] HELICAL SPRING FOR PRODUCING ARTIFICIAL REVERBERATION .[72] Inventor: Werner Fidi, Baden near Vienna,

Austria [73] Assignee: Akustische U. Kino-Gerate Gesellschaft m.b.H., Vienna, Austria [22] Filed: Aug. 10, 1970 [21] Appl. No.: 62,442

[30] Foreign Application Priority Data Aug. 19, 1969 Austria ..7934/69 [52] US. Cl ..267/161 [51] Int. Cl. ..Fl6f 1/34 [58] Field of Search ..267/16], 182

[56] I References Cited UNITED STATES PATENTS R13,699 3/1914 Denis ..267/161 3,389,642 6/1968 Robinette ..267/161 Primary Examiner-James B. Marbert Attorney-John J. McGlew and Alfred E. Page [57] ABSTRACT A helical spring for producing artificial reverberation, with the frequencies to be reverberated being impressed thereon in the form of torsional vibrations, has individual turns, at random locations therealong, deformed irregularly from a normally circular configuration. Portions of the deformed turns may be deformed outwardly from the normally circular configuration or deformed inwardly therefrom, or in both directions, but in the plane of the circular configuratron.

10 Claims, 6 Drawing Figures PmENTEnncnomz 8.691.059

INVENTOR.

WERNER 1 W HELIC AL SPRING FOR PRODUCING ARTIFICIAL I REVERBERATION BACKGROUND OF THE INVENTION I jected to transit time effects and to reflections, to

produce a vibration pattern which is similar to that of natural reverberation and which is once again converted into electrical vibrations by means of further electro-mechanical transducer means. The artificial reverberation thus obtained normally is mixed with the signal, which has not been modified by reverberation, and is radiated, for example by a loudspeaker.

To obtain the desired result, certain fundamental requirements must be satisfied, as follows:

1. Periodicity in the time spectrum and in the frequency spectrum must be avoided.

2. There must be a high density of the pole/zero configuration in the frequency response with-a quasi high density in the pulse/time spectrum.

3. The reverberation time should decrease towards the low frequencies as well as towards the high frequencies.

4. The mean frequency response also should diminish towards low frequencies as well as towards high frequencies.

A homogeneous, uni-dimensional structure, as represented by a helical spring, cannot satisfy easily these conditions, particularly the first mentioned condition, since such a helical spring supplies a purely periodic frequency response in accordance with the following equation:

was

Furthermore, such a spring supplies a purely periodic time spectrum in accordance with the following equationr In the foregoing equations, T is the delay period, and b is the attenuation of successive pulses.

For the purpose of destroying the aforementioned periodicity, it has been proposed to provide the wire, which forms the helical spring, with an irregular surface, for example by etching, so that statistical changes" It has also been attempted to attain a continuous 4 dispersion by a uniform change in the diameter of successive convolutions of the spring. However, this measure results in an increased delay of the low frequencies.

SUMMARY OF THE INVENTION This invention relates to helical springs for producing artificial reverberation and, more particularly, to a novel and improved such helical spring in which the above-mentioned disadvantages are avoided and which can be used to construct a reverberation apparatus capable of producing artificial reverberation which is very similar to natural reverberation.

In .particular, the invention provides an improvement in the range below 200 Hz, because the features of the invention destroy the periodicity in the frequency spectrum as well as in the pulse spectrum, at low frequencies. In accordance with the invention, individual spring turns, selected at random in a helical spring for producing artificial reverberation, and on which the frequencies to be reverberated are impressed in the form-of torsional vibrations, are deformed irregularly from a normally circular configuration.

The deformations may consist of inward or outward or both deflections of the spring wire, from the normally circular configuration, and of varying magnitude or intensity, the deflections being disposed substantially in the surface plane of the undeformed circular spring turn.

In an appropriate embodiment of the invention, the helical spring has a surface which is rendered irregular by etching, since only this procedure is suitable for producing a reverberation spring which operates reliably over the entire transmission range. However, if the frequency range is subdivided and a separate spring is associated with each subdivision, it is possible to dispense with an irregular surface of the spring wire for the range below 200 Hz. This procedure involves only a slight loss of quality.

An object of the invention is to provide an improved helical spring for producing artificial reverberation with the frequencies to be reverberated being impressed on the spring in the form of torsional vibrations.

Another object of the invention is to provide such a spring in which individual turns, at random locations therealong, are deformed irregularly from a normally circular configuration.

A further object of the invention is to provide such a spring which has a surface rendered irregular by etching.

Another object of the invention is to provide such a spring in which the randomly located individual turns are deformed inwardly, outwardly, or in both directions from a normally circular configuration.

For an understanding of the principles of the invention, refefence is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings. I

BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings: FIG. 1 is an elevation view of an elliptically deformed spring wire turn;

FIG. 2 is anelevation view of an inwardly deformed spring wire turn; and

FIGS. 3a 3d are views, similar to FIGS. 1 and 2, illustrating further, but not limiting, configurations which the deformations may take.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the invention, spring turns which are statistically selected over the length of the entire spring, are provided with inward, outward, or both deflections of different magnitude or intensity, so that the mass, as well as the stiffness, of the thus deformed turns can be increased as well as reduced. In dependence on the degree of deformation, it is possible for the mass, as well as the stiffness, of the individual spring turns or convolutions to be varied, in practice almost at will, the stiffness being reduced if the spring turn is deformed in accordance with FIG. 1. However, if the spring turn is deformed in accordance with FIG. 1, the mass, and thus the moment of inertia, of the turn is increased.

On the other hand, if the spring turn is deformed as indicated in FIG. 2, the mass will be reduced and the stiffness will be increased.

These modifications or deformations appropriately are performed on the completed spring, that is, on a spring which has been coiled and has had its surface etched. The overall length of each deformed spring turn is thus approximately equal to the length of an undeformed spring turn or convolution.

As a first approximation, it is possible to regard all inward bends, starting from a normally circular form of a spring turn or convolution, as increasing the stiffness and reducing the mass of the deformed turn, while outward bands, in all cases, reduce the stiffness, but, in dependence on the shape, the moment of inertia may remain the same, may be increased, or in some cases may be decreased. However, since usually it is necessary only to provide deformations in accordance with FIGS. 1 and 2, of different intensities to produce the desired effect, it follows that the masses or the moments of inertia, respectively, are also increased with outward deformations.

It is, of course, possible for the deformations to be performed as desired within wide limits as can be seen from the example of FIGS. 3a 3d, which represent only a small selection of possible shapes.

Thus, in FIG. 3a, the spring turn has three inward deformations of approximately the same magnitude, whereas in FIG. 3a, the spring turn again has three inward deformations but of different magnitudes.

FIG. 3c illustrates a spring turn having both outward and inward deformations of different magnitudes, and FIG. 3d illustrates a deformed spring turn having a single outward deformation and three inward deformations two of which are of the same magnitude and the third of which is of a larger magnitude or intensity.

The essential feature is that the deformed spring turns or convolutions are distributed statistically along the spring, the required random pattern being imade uate exte t.

ile spec IC embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a helical coil spring for producing artificial reverberation, with the frequencies to be reverberated being impressed thereon in the form of torsional vibrations, the improvement comprising, in combination, individual turns of said spring, at random locations therealong, having irregular deformed portions deviating from a normally circular configuration.

2. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 1, in which said individual turns are deformed irregularly in substantially the surface plane of the normally circular convolution.

3. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 1, in which the deformations of said individual turns are deflections of differing extent.

4. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 3, in which said deflections are disposed substantially in the surface plane of the normally circular turn configuration.

5. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 4, in which the deformations of individual turns are inward deflections thereof.

6. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 4, in which the deformations of the individual turns are outward deflections thereof.

7. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 4, in which the deformations of the individual turns are inward and outward deflections thereof.

8. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 1, in which the surface of said spring is irregular.

9. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 8, in which said irregular spring surface is an etched surface.

10. A reverberator adapted to be stimulated to torsional vibrations by electromechanical converters, comprising at least one helical coil for generally circular configuration having a plurality of irregular deformations deviating from a normally circular configuration. 

1. In a helical coil spring for producing artificial reverberation, with the frequencies to be reverberated being impressed thereon in the form of torsional vibrations, the improvement comprising, in combination, individual turns of said spring, at random locations therealong, having irregular deformed portions deviating from a normally circular configuration.
 2. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 1, in which said individual turns are deformed irregularly in substantially the surface plane of the normally circular convolution.
 3. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 1, in which the deformations of said individual turns are deflections of differing extent.
 4. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 3, in which said deflections are disposed substantially in the surface plane of the normally circular turn configuration.
 5. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 4, in which the deformations of individual turns are inward deflections thereof.
 6. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 4, in which the deformations of the individual turns are outward deflections thereof.
 7. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 4, in which the deformations of the individual turns are inward and outward deflections thereof.
 8. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 1, in which the surface of said spring is irregular.
 9. In a helical coil spring for producing artificial reverberation, the improvement claimed in claim 8, in which said irregular spring surface is an etched surface.
 10. A reverberator adapted to be stimulated to torsional vibrations by electromechanical converters, comprising at least one helical coil for generally circular configuration having a plurality of irregular deformations deviating from a normally circular configuration. 